Antifriction corrosion-resisting steel



Patented Dec. 8, 1931 UNITED STATES PATENT OFFICE,

FRANK B. PALMER. OF READING, PENNSYLVANIA. ASSIGNOR TO THE GARPEN'I'EB STEEL COMPANY, OF READING, PENNSYLVANIA, A. GORCPORATION OF NEW JERSEY mn'nrcrron' oortaosron-nnsrsrme sin-1m.

H'o Drawing.

- My invention has for its object the production of alloy steels of the corrosion or scale resisting class, which will be characterized by what may be best termed anti-friction 5 properties as evidenced by their behavior when in kinetic contact with tool material employed in their fabrication or with surface material in connection with which they are used.

In the corrosion and scale resisting or stainless steels to which my invention particularly relates; the element ,chromium is used in high percentages relative to the iron or steel base, with or without other alloying elements such as nickel, copper, molybdenum,

silicon or tungsten; the minimum chromium content for scale resisting quality being about 2.00%, and for corrosion resisting quality about 8.00%. It has been found however that all of these high-chromium steels incidentally possess a characteristic quality which is not onlyunsought for, but which is generally objectionable; namely, what may be termed a gummy or sticky quality which causes such steels to adhere to other materials with which they are brought into kinetic contact. This high-friction quality of these corrosion resisting steels impairs their machinability independently of recognized anti-machining qualities such as inherent hardness or a tendency'to work-hard 1 en; the high-friction quality referred to causing sticking of chips to tools or of fragments of the metal to abrasive mediums, with result-' ing difficulties and imperfections; and also impairing the usefulness of properly finished articles made therefrom so far as kinetic friction is involved,-by tending tocause cutting or galling and even freezing or seizing of the contacting surfaces. 7

It is generally knownthatthis high-friction quality of these high-chromium corrosion resisting steels is much greater than it is in ordinary straight carbon steels, and that it is not due to differences in surface hardness or physical properties as ordinarily determined, but seems to be inherent in the analysis of these high chromium alloy steels.

The high-friction characteristics of such the high-friction qualities which are resent Application filed Ianuary 17, .1928. serial No. 247,462.

steels are. evidenced clearly by the following examples:

In order to satisfactorily cold-draw wire, tubing, etc., from usual high-chromium steels it is necessary that they be plated with a non-ferrous metal so as to avoid actual contact with the drawing dieotherwise= the metal will adhere to the die. Bolts and nuts may even become frozen upon screwing them together by hand. In machining, ch1ps are apt-to adhere so firmly to'the tool as to seriously interfere with the work. In movin' parts operating at elevated temperatures sue as for instance high-pressure gate valves and poppet valves, made of this otherwise desirable material, this high-friction quality tends to cause galling, stickin or freezing. The field of satisfactory use ess of highchromium corrosion resisting steels is thus materially reduced. 1 The above exam les are typical of areal problem involved 1n the commercial use ofhigh chromium corrosion and scale resisting steels for which there has hitherto been no adequate solution. The purpose of my invention is to overcome these disadvantages, which have been long accepted as inherent inv these steels, and to attain this purpose without sacrifice of desired qualities; the invention consisting in the production of a new alloy steel as hereinafter fully described, in whichthe desired corrosion resisting ualities are retained and this deleterious ighfriction quality is substantially neutralized.

In all stainless and other high-grade steels, V the metalloid sulphur appears incidentally, but is hardly tolerated'in quantities exceeding about 05%; though in the common straight carbon product known as screw stock, the sulphur may be permitted as high as 15% to improve machinability. I have found that sulphur, when incorporated in relatively large amounts in a chromium corrosion of scale resisting steel, will offset by reason of the high chromium. t was found in the development of this invention that percentages of sulphureven as high as that used in common screw stock--had little effect on either the machinability or-fric- I characteristics of high-chr m m cor".

rosionfl' resisting steels. When quantities of s'ulpliur -insexcess of about .15 were introduced into a c'orrosion resisting steel base,

it. was found that the hot working qualities. a were -*so "deereased. as to make the satisfactory forging or rolling of the resultant steelsvery difiicult; but' ;in spite of this fact I have I meltedthese Icorrosion resisting alloys with sulphur-contents ranging from 15% up to content of.30% or more. Between 15% and 30%; sulphur the improvementis progressive, ;-the results becomingentirely satisfactory" at about 130% sulphur, and not being proportionately improved by larger quantities of sulphur. When the chromium content-fal1s1below 10% into the rangeprincipally. used for scale resisting purposes, the

fpercent'age of-sulphur required for anti-frie 'tion qualities may be reduced to as low as My proved alloy as described above may be satisfactorily employed for castings with desired anti-friction effect but. for malleable steels objectionable red-shortness caused by resulting iron-sulphide is aptto result. In-

experimenting in a crucible furnace with a view to overcoming this bad effect of the relatively large content of sulphur required to offset the high-friction quality of high chro mium steels, primarily dealt with, I have found that this can be quite satisfactorily accomplished by proper addition of zirconium, an element known to decrease red-shortness due to high sulphur, and a small quantity of which I have ascertained may be effectively and satisfactorily employed in these highchromium corrosion resisting steels, in connection with the high sulphur content which I have empl yed to neutralize their high friction quality; with the desired result of correcting the red-shortness otherwise produced, and without impairing the desired effect of the sulphur or without deleterious effeet upon the desired qualities imparted by .the high-chromium of such steels. I have found, in the crucible furnace product made, that the addition of about of zirconium to the molten bath fully corrects the redshortness produced by a sulphur content of the residual. content of zirconiumin the steel after loss in the molten bath being about 12% which combines with the sulphur as commonly understoodto form a finely di vided slag like inclusion. The required zirconium is readily introduced by using silicon-zirconium without detrimental silicon effect the silicon in .fact serving, to supplement the chromium used.

The percentage-of zirconium employed vacutt' hee 2% rice with thesulphur content a moderate excessof zircomum producesno harmful efditions to the metal, or :by' manganese and zirconium jointly, but because of the collateral effects of high manganese, I prefer to use zirconium in most instances.

A typical example ofimy; improved alloy steel has been variously used as hereinafter set forth, so as to clearlyfdemonstrate how effectively my-invention has neutralized the high-friction characteristic of high chromi um corrosion resisting steels, with full retention'of desired corrosion resistin' qualities; the analysis of this exam le so ar as main elements are concerned, being as follows:

Per cent Carbon .10 Chromium 14.00 Sulphur- .30 Zirconium .12

Hot rolled wire rods made from steel of this analysis, have been cold drawn without any metallic coating-in the same manner as straight carbon steel and with equal avoid ance of seizing, galling or scratching. Steel of the same analysis has been subjected to turning, milling, drilling, tapping and threading operations by ordinary steel-cutting tools, wlth the same facility and smoothness of finish as straight-carbon steel, the edges of the tools remaining equally adhering bugs. Similar cylindrical weights made respectively from steel of the above analysis and from hke high-chromium steel with minimum sulphur and zirconium elements, whenplaced on a polished inclined plane have shown; markedly quicker starti and sliding movement by the former. en subjected to salt-water spray testing conditions, my improved alloy steel shows the same corrosion-resisting quality as does like high-chromium steel which is minus the sulphur-zirconium addition.

The above analysis-is not to restrict in any way the scope of my invention as I have similarly added sulphur and zirconium 'to corrosion resisting steels of both higher and lower chromium contents both with and with out the addition of other elements such as silicon, copper and nickel, and the improvement was of the same order, it being readily understood that the desired anti-frictional effect is conferred by the considerate providing of an abnormally high sulphur content, and further that these high-chromium, highsulphur steels are made more malleable by the coacting zirconium element as described. My improved alloy can be satisfactorily made in an electric furnace as usual, the sulphur and zirconium being readily added to the base alloy steel as determined by good steel making practice; it being readil understood that an excess amount of sulp ur and zircomum must be used 1n order to secure a deslred yield, and my present experience showing apparent advantages in dumping a portion of lump sulphur' with a. smothering layer of silicon-zirconium orferro-zirconium, upon the bottom of the ladle as the heat is tapped, and throwing a further supply of sulphur into the flowing stream, this method yieldin about fifty per cent of the quantity of sulp ur and zirconium used.

4 What I claim is:

1. As a composition of matter, a corrosionresisting alloy steel containing essentially be tween 7% and 30% of chromium, an be tween 15% and l.80% of sulphur, and char-.

acterized by an: iriction quality.

2; As a composition of matter, a corrosionresisting alloy steel conltatining essentially between 7% and 30% of chromium, between .15-% and 1.80% of sulphur, and between .05 and 2.00% of zirconium, and characterized by anti-friction'quality.

3. As a composition of matter, a corrosionresisting alloy steel containing essentially between 10% and 20% of chromium, and between .15% and 1.00% of sulphur, and characterized by anti-friction-quality.

4. As a composition of matter, a corrosionresisting alloy steel containing approximate- 'tween 8% and 20% of chromium, an

In testimony 1y 14% of chromium, and .30% of sulphur, and characterized by anti-friction-quality.

5. As a composition of matter, a corrosionresisting alloy steel containing essentiallg Re; tween 15% and,.25%- of sulphur, and characterized by anti-friction quality.

whereof I aflix my si -ature.

. FRANK R. P R. 

